Tape cassettes for business use are enlarged in size for improving the picture quality and for extending the recording time. For example, a tape cassette for digital recording and playback may have external dimensions of a lateral width of 366 mm, a longitudinal width of 206 mm and a thickness of 33 mm. Its weight is also extremely heavy.
As a tape cassette receiving housing for receiving a tape cassette for business use as the above, one shown in FIG. 22 is known.
FIG. 22 is a perspective view of a conventional tape cassette receiving housing 101.
The tape cassette receiving housing 101 is equipped with a housing proper portion 102 for receiving a tape cassette such as a digital video tape cassette, a lid portion 103 for opening or closing an opening portion of the housing proper portion 102, and a pair of positioning shaft portions (engaging projection portions) 104, 105 formed on an upper surface of the housing proper portion 102.
The shaft portions 104, 105 are cylindrically formed so as to be smaller in diameter than reel driving holes 114, 115 of a supply reel 112 and a take-up reel 113 of the tape cassette 111. 116 . . . 116 are gear-like driving ribs constituting the reel driving holes 114, 115.
When the tape cassette 111 is inserted into the housing proper portion 102, as shown in FIG. 20, the shaft portions 104, 105 penetrate into the reel driving holes 114, 115 of the supply reel 112 and the take-up reel 113 of the tape cassette 111, 115 and limit the movement of the tape cassette 111, thereby protecting the tape cassette from the impact upon falling or the like.
Furthermore, FIG. 23 is a sectional view of a condition in which the tape cassette 111 is received in the tape cassette receiving housing 101. In FIG. 23, 117 is a magnetic tape, 118 and 119 are upper and lower flanges of the supply reel 112 and the take-up reel 113. 120 and 121 are upper and lower shells of the tape cassette 111. 122 is a reel holder attached to the upper shell 120. 123 is a reel spring. 124 is a reel plate.
FIG. 24 is a sectional view showing an interior of the tape cassette 111.
In FIG. 24, 125 is a leader tape, and an end portion of the leader tape 125 is clamped by a clamper 126 of the take-up reel side, between the clamper 126 and a clamper-attaching portion 128 formed on a shaft portion 127 of the take-up reel 113. 131 and 132 are first and second ratchet mechanisms placed on the outer sides of flanges of the supply reel 112 and the take-up reel 112.
The first ratchet mechanism 131 comprises a ratchet tooth 135 formed on an outer periphery of the flange of the supply reel 112 and a ratchet pawl 134 which is to be meshed with the ratchet tooth 133.
Furthermore, the second ratchet mechanism 132 comprises a ratchet tooth 135 formed on an outer periphery of the flange of the take-up reel 113 and a ratchet pawl 136 which is to be meshed with the ratchet tooth 135.
Furthermore, as shown in FIG. 22, when the lid is in a closed condition, the ratchet pawl 134 of the first ratchet mechanism 131 is engaged with the ratchet tooth 133 formed on the supply reel 112, thereby preventing the supply reel 112 from rotating in a tape delivery direction (a clockwise direction in FIG. 24).
On the other hand, the ratchet pawl 136 of the second ratchet mechanism 132 is engaged with the ratchet tooth 135 formed on the take-up reel 113, thereby preventing the take-up reel 113 from rotating in a tape delivery direction (a counter-clockwise direction in FIG. 24).
The above conventional tape cassette receiving housing has the following problems.
(1) When an impact force in a direction (hereinafter referred to as a lateral direction) perpendicular to the axial direction (axial direction of the shaft portions 104, 105) is added by an impact upon falling or the like, the shaft portions 104, 105 function effectively so as to suppress the movement of the supply reel 112 or the take-up reel 113 in the lateral direction. However, when an impact force in the axial direction (referred to as a longitudinal direction) is added, the shaft portions 104, 105 hardly function. Thus, the supply reel 112 or the take-up reel 113 moves in the longitudinal direction in a manner to come off the shaft portions 104, 105. PA1 (2) When the supply reel 112 or the take-up reel 113 is in an inclined condition as shown in FIG. 25 and moves in the longitudinal direction by the addition of an impact force in the longitudinal direction, end portions of the upper and lower flanges 118, 119 of the supply reel 112 or the take-up reel 113 are brought into abutment with the upper and lower shells 120, 121. With this, the end portions of the upper and lower flanges 118, 119 are deformed, thereby damaging tape edges of the magnetic tape 117 positioned at the end portions. PA1 (3) When a force in a rotational direction is added to the supply reel 112 and the take-up reel 113 by the vibration upon the product transportation or the like, the end portion of the leader tape 125 may have slipped off from a space between the clamper-attaching portion 128 formed on the shaft portion 127 of the take-up reel 113 and the clamper 126 attached to the attaching portion 128.
The reason will be explained as follows.
The supply reel 112 and the take-up reel 113 try to alternately rotate in a tape delivery direction and a tape take-up direction by the vibration upon the production transportation.
However, as is mentioned hereinabove, the supply reel 112 and the take-up reel 113 are prevented by the first and second ratchet mechanisms 131, 132 from rotating in the tape delivery direction and permitted to rotate only in the tape take-up direction.
By the way, upon shipping of the product, the magnetic tape is scarcely wound around the take-up reel 113, and, in contrast, it is fully wound around the supply reel 112. Therefore, a difference will occur in moment of inertia, between the take-up reel 113 and the supply reel 112, and a force to rotate in the tape take-up direction of the supply reel 112 is far greater than a force to rotate in the tape take-up direction of the take-up reel 113.
By the way, as is mentioned hereinabove, the rotation in the tape delivery direction of the tape take-up reel 113 is suppressed by the second ratchet mechanism 132.
Therefore, the leader tape 125 of which end portion is clamped by the clamper 126 to the take-up reel 113 is intermittently pulled by the supply reel 112.
With this, for example, the end portion of the leader tape 125 relatively easily comes off the space between the clamper-attaching portion 128 and the clamper 126, in relation to a distance for clamping the leader tape or the like between the clamper-attaching portion of the shaft portion 127 of the take-up reel 113 and the clamper 126 attached to the attaching portion 128.
Furthermore, as is mentioned hereinabove, the supply reel 112 and the take-up reel 113 are to be rotated only in the tape take-up direction by the first and second ratchet mechanisms 131, 132. Therefore, the inner diameter side of the magnetic tape 117 which is wound about the supply reel 112 is pulled to the tape take-up side, and the outer diameter side moves in the tape delivery direction by the rotation of the take-up reel 113.
Therefore, a so-called cinching will occur at a position where the balance of the tape winding pressure is bad.